Multicell Battery monitoring and balancing with AVR

Abstract

Today Lithium Ion batteries are extensively used in all kinds of electronic equipment due to its superior properties. However, Lithium Ion batteries need to have all the individual cells monitored to ensure the safety and long life time. This master thesis' objective is to design a managing system for a ten cell Lithium Ion battery with an Atmel AVR microcontroller. The main challenge was to scale down the high voltage level a 10 cell battery has and still maintain accuracy when reading this voltage with the AVR. This was solved by using current sense monitors which can handle large common mode voltages. Hardware was made to show proof of concept. It was found that the scaling circuitry had an accuracy of 46mV. In competition with other single chip devices, some other methods have to be found. The design in this thesis is physically too large and too expensive to be of any commercial use. However some other methods worth looking into have been proposed in the last chapter.